Add clearOutputs() method to ISharedCodeCell

[Darshan808]

References jupyterlab/jupyterlab#17632

Description

This PR introduces a clearOutputs() method to the ISharedCodeCell interface and its implementation in YCodeCell. This method provides a clean and direct way to remove all outputs from a code cell in the shared model.

This change is motivated by a bug in JupyterLab where uncoalesced stream outputs can persist in the cell output area. The root cause is that the frontend coalesces outputs, but the shared model retains multiple entries, making it tricky to clear all outputs using updateOutputs() when their lengths differ.

[davidbrochart]

Missing origin?

[Darshan808]

The origin parameter wasn’t exposed in the updateOutputs() method, so I followed the same pattern and didn’t expose it in clearOutputs() either.

jupyter_ydoc/javascript/src/api.ts

Lines 569 to 573 in d989856

	updateOutputs(
	start: number,
	end: number,
	outputs: Array<nbformat.IOutput>
	): void;

I’m not entirely sure about the reasoning behind this, but if exposing it in the interface is something we should do, I’m happy to make that change.

[krassowski]

What do we need origin for in the first place? E.g. this one does not have origin:

jupyter_ydoc/javascript/src/ycell.ts

Lines 803 to 809 in b9168fd

	setOutputs(outputs: Array<nbformat.IOutput>): void {
	this.transact(() => {
	this._youtputs.delete(0, this._youtputs.length);
	const newOutputs = this.createOutputs(outputs);
	this._youtputs.insert(0, newOutputs);
	}, false);
	}

[krassowski]

But this one does:

jupyter_ydoc/javascript/src/ycell.ts

Lines 814 to 825 in b9168fd

	removeStreamOutput(index: number, start: number, origin: any = null): void {
	this.transact(
	() => {
	const output = this._youtputs.get(index);
	const prevText = output.get('text') as Y.Text;
	const length = prevText.length - start;
	prevText.delete(start, length);
	},
	false,
	origin
	);
	}